IEEE 802.15 describes a communication architecture, which may enable communicating devices (DEVs) to communicate via wireless personal area networks (WPANs). Many DEVs utilized in WPANs are small or handheld devices, such as personal digital assistants, portable computers, or consumer electronics devices such as digital video recorders or set top boxes. IEEE 802.15 is a short-range wireless communications standard that enables connection between consumer and computer equipment while eliminating wires. IEEE 802.15 WPAN DEVs may utilize frequencies in the 57 GHz to 66 GHz range for communication.
A plurality of communicating DEVs in a WPAN environment may comprise a network known as a piconet. One of the DEVs in a piconet may function as a piconet coordinator (or controller), or PNC. The PNC may provide overall coordination for the communication between DEVs in a piconet. The piconet may comprise the PNC and DEVs, which are associated with the PNC.
Communications between communicating DEVs in a WPAN may occur within time intervals referred to as superframes. The superframe may comprise a plurality of segments. In a first superframe segment, the PNC may transmit one or more beacon frames. The beacon frame may enable recipient DEVs to identify the PNC. The beacon frame may also enable recipient DEVs to identify other DEVs, which are currently associated with PNC within the piconet. In addition, a beacon frame may indicate time durations within the current superframe during which assigned DEVs may transmit and/or receive signals via a wireless communication medium. These time durations may be referred to as time slots. The time slot assignments may be in response to requests received from the DEVs during one or more previous superframes.
A second superframe segment may comprise a contention access period (CAP). The starting time instant and time duration of the CAP may be communicated within the preceding beacon frame. During the CAP, the DEVs may respond to the beacon frames by communicating with the PNC to establish an association within the piconet. Associations established during a current superframe may be reported via beacon frames in one or more subsequent superframes.
The DEVs within the piconet may also utilize the CAP to communicate data to other DEVs. Communicating DEVs may attempt to gain access to the wireless communication medium before attempting to transmit data. The collision sense multiple access with collision avoidance (CSMA/CA) protocol is typically utilized by communicating devices for wireless medium access. During the CAP, a DEV seeking medium access, an originating DEV, may transmit a request to send (RTS) frame. The RTS frame may be addressed to a destination DEV but the RTS frame may be received by other DEVs. The destination DEV may respond to the RTS frame by transmitting a clear to send (CTS) frame. The originating DEV and destination DEV may subsequently commence communication via the wireless medium. The communications may, for example, involve the transmission of data frames between the originating DEV and the destination DEV. Direct communications between an originating DEV and a destination DEV during the CAP are typically intermittent communications, which comprise relatively short time durations. In accordance with the CSMA/CA protocol, other DEVs that receive the RTS frame transmitted by the originating DEV may refrain from transmitting signals via the wireless medium during these communications. When an originating DEV seeks to reserve access to the wireless medium for longer time durations, the originating DEV may transmit an RTS frame to the PNC during the CAP. The PNC may respond to the originating RTS frame by sending an acknowledgment frame that comprises a time allocation slot.
A third superframe segment may comprise a channel time allocation (CTA) period. The CTA period may comprise one or more CTA time slots. During the CTA period, the PNC may assign and/or schedule a set of CTA time slots to one or more DEVs within the piconet. The PNC may communicate a time allocation slot to an assigned DEV during the CAP that identifies a specific CTA time slot. During the assigned CTA time slot the assigned DEV may be granted reserved access to the wireless communication medium. The assigned DEV may utilize the assigned CTA time slot to engage in communications with one or more destination DEVs. Other DEVs, which are not engaged in communications with the originating DEV, may refrain from transmitting signals via the wireless communication medium during the assigned CTA time slot. In conventional piconet systems, an individual CTA time slot is assigned to a single DEV. Thus, a single DEV may transmit signals via the wireless communication medium during a given CTA time slot.
The CTA period may also comprise a management CTA (MCTA) period. During the MCTA period, the DEVs may request CTA time slot assignments from the PNC. The PNC may respond to CTA time slot allocation requests received in the current superframe by making CTA time slot assignments for one or more subsequent superframes. The time slot assignments may be reported via beacon frames transmitted during the respective subsequent superframes.
The 57 GHz to 66 GHz frequency band may be utilized by different types of DEVs. The different types of DEVs may be utilized in connection with a variety of applications, which have different requirements.
The DEVs utilized in connection with digital video applications, for example video display, digital video recorder (DVR) and/or set top box (STB) devices may operate at data throughput rates that are in excess of 3 Gbps. Wireless communications between the video display, DVR and/or STB DEVs may involve transmission and reception of signals that traverse non line of sight (NLOS) signal propagation paths.
Portable computer and docking station DEVs may also operate at data throughput rates that are in excess of 3 Gbps. Wireless communications between portable computers and docking station DEVs may occur over line of sight (LOS) and/or NLOS signal propagation paths.
Hand-held DEVs may operate at data throughput rates that are in excess of 1 Gbps. The Hand-held DEVs may communicate wirelessly in connection with file sharing, sharing of digital audio content, digital video content and/or digital multimedia content, for example. Wireless communications between the hand-held devices typically occur over LOS signal propagation paths.
Wireless communications between hand-held and portable computer and/or network attached storage (NAS) DEVs may occur within the context of data synchronization applications. For example, a hand-held DEV may transmit data stored within the hand-held DEV to a personal computer DEV to enable data synchronization between the data stored in the hand-held DEV and the corresponding data stored in the personal computer DEV. The data stored in a personal computer or NAS DEV may then be accessed via a network. Wireless communications between hand-held DEVs and portable computer and/or NAS DEVs may involve data throughput rates that are in excess of 1 Gbps and typically occur over NLOS signal propagation paths.
Within a given DEV, applications may operate within the broader construct of a protocol reference model (PRM). The PRM may comprise a series of layers that enable communication between DEVs. For example, the PRM may comprise an application layer. The application layer within the PRM may correspond to a data source. Other layers within the PRM may cooperate with the application layer to partition the data from the data source into protocol data units (PDUs), for example, packets or frames, which comprise blocks of bits generated by the data source. At the physical (PHY) layer, signals may be generated that enable the data to be transmitted across a wired and/or wireless communication medium. The complexity of the operations performed by the PHY layer may be determined based on the application and corresponding requirements. Thus, different DEV types, which are utilized in connection with different applications, may comprise different levels of PHY complexity.